The research under the tenure of this grant will be aimed at elucidating the mechanisms of interaction between the cytosol and nuclear binding of corticosterone, and will provide information concerning the nature and functional properties of the specific brain corticosterone nuclear receptor. This information is essential for our understanding of how hormones exert regulatory and behavioral effects on the central nervous system. Therefore, the following objectives will be accomplished: 1. Demonstrate the true binding (gel chromtography and equilibrium dalysis) of 3H-corticosterone to neuronal nuclei after incubation with a labeled-brain cytosol complex. 2. Determine what effect temperature, time, ionic strength, enzymes, and hormones may have on cytosol to nuclear binding mechnisms. 3. Study the interaction of 3H-corticosterone cytosol receptor complex in vitro with chromatin, acidic, neutral and basic proteins isolated from rat brain nuclei, and determine if the corticosterone-cytosol complex binds to a greater degree to chromatin than to one of these other classes of compounds. 4. Determine the role of tissue specificity on the cytosol to nuclear binding mechanism; that is, will th cytosol receptor from various tissues (thymus, liver kidney) initiate nuclear binding in brain nuclei.